It really depends on the variety. Some can get quite tall and lanky. If you want to make sure it gets bushy, I would suggest pinching it a bit. It will bush out then.

Tracy

Don't fertilize. I have found the richer the soil the smaller the plant and flower production. I have had my west facing plants to get about 5 feet with stalks about 3 inches around. Again, it depends on the variety. I grow them in rows and use the foligae in arrangements.